“but it does cost money to store”
How much storage do you need? Thirty pounds of gold coins can fit in a small case and has half a million USD value at today’s gold prices.
Perhaps the author means the cost to protect and insure the gold which may not have much value in an apocalyptic scenario anyway.
Those that stash under the mattress will also have to pay for certifying the gold at time of resale. Another thing for independant owners is the high buy/sell price. Other investments --say, stocks-- we're talking a percent or so (including commissions) but it's many times that for gold.